Image forming apparatus

ABSTRACT

In an image forming apparatus in which a plurality of feeders can be added, a main body driving portion is provided in an apparatus main body and a drive feeder having a driving portion is provided among the plurality of feeders. The main body side driving portion drives an adjacent feeder, and the driving portion of the drive feeder drives the drive feeder and a feeder adjacent to the drive feeder. In the image forming apparatus, it is unnecessary to provide a dedicated driving portion in an additional feeder, it is also unnecessary to supply a driving force to the additional feeder from the apparatus main body. Therefore, no limitation is required of the additional feeder, and cost increase for an entire product can be prevented.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an image forming apparatus and, in particular, to an image forming apparatus in which a plurality of feeders that have a sheet containing portion for containing sheets and a sheet feeding portion for feeding a sheet from the sheet containing portion, respectively, can be added to an apparatus main body provided with an image forming portion in a vertical direction of the image forming apparatus.

[0003] 2. Description of Related Art

[0004] Conventionally, among image forming apparatuses such as a copying machine and a printer mainly of low to medium speed classes, there is one in which a plurality of feeders that are provided with a sheet containing portion for containing sheets to be supplied to an image forming portion and a sheet feeding portion for feeding a sheet from the sheet containing portion, respectively, can be added in its vertical direction below an apparatus main body including the image forming portion.

[0005]FIG. 11 is a view showing an example of a state in which feeders are added in such a conventional image forming apparatus. In the figure, reference numeral 90 denotes an apparatus main body provided with a image forming portion (not shown) and 92 denotes a feeder provided below the apparatus main body 90. In this feeder 92, there are provided a sheet containing portion (not shown) for containing sheets to be supplied to the image forming portion and a sheet feeding portion (not shown) for feeding a sheet from the sheet containing portion. In addition, reference numeral 91 denotes a motor functioning as a driving portion provided in the apparatus main body. This motor 91 supplies a driving force to the feeder 92 in the apparatus main body. Then, the sheet feeding portion is driven by the driving force from this motor 91, and the sheet contained in the feeder 92 is fed to the image forming portion.

[0006] Reference numerals 93 to 95 denote additional feeders added as an option below the apparatus main body 90. In each of these additional feeders 93 to 95, there are provided a sheet containing portion (not shown) for containing sheets to be supplied to the image forming portion, a sheet feeding portion (not shown) for feeding a sheet from the sheet containing portion, and respective sheet feeding motors 96 to 98 functioning as a driving portion for driving the sheet feeding portion. In addition, in each of the additional feeders 93 to 95, there are provided a conveying path (not shown) for conveying a sheet fed from the feeder below it upward.

[0007] Then, the plurality of additional feeders 93 to 95 can be added in the vertical direction in this way, and various sheets (with different sizes, colors and the like) are contained in these additional feeders 93 to 95, whereby images can be formed on the various sheets desired by a user.

[0008] In addition, FIG. 12 is a view showing another state in which feeders are added in the conventional image forming apparatus. In the figure, reference numeral 100 denotes an apparatus main body having an image forming portion and 102 denotes a feeder provided below the apparatus main body 100. Further, reference numeral 101 denotes a main motor that is a driving portion provided in the apparatus main body. This main motor 101 supplies a driving force to the feeder 102.

[0009] On the other hand, reference numeral 103 denotes an additional feeder optionally added below the apparatus main body 100. The additional feeder 103 is provided with a sheet containing portion (not shown) for containing sheets to be supplied to the image forming portion and a sheet feeding portion (not shown) for feeding a sheet from the sheet containing portion. Further, this additional feeder 103 is not provided with a driving portion for driving the sheet feeding portion. The sheet feeding portion is driven by the main motor 101 of the apparatus main body 100. With such a structure, cost reduction of the additional feeder 103 can be realized.

[0010] However, the following deficiencies and disadvantages occur in the conventional image forming apparatus in which such additional feeders can be added.

[0011] That is, if the image forming apparatus is constituted to be provided with the dedicated sheet feeding motors 96 to 98 in the additional feeders 93 to 95, respectively, as shown in FIG. 11 described above, although a multi sheet feeding structure for coping with various sheets can be realized, cost increase as an entire product is inevitable.

[0012] In addition, in the structure for supplying a driving force to the additional feeder 103 from the apparatus main body 100 as shown in FIG. 12 described above, it is difficult to balance costs with the number of feeder stages to be set. That is, if a plurality of feeders can be mounted, the main motor 102 of the apparatus main body 100 should have a large capacity in order to drive each feeder. This causes cost increase of a standard model (apparatus main body 100) without additional feeders, resulting in large burden on a user who uses only the standard model. Further, if the capacity of the main motor 102 is limited attaching importance to costs in the standard model (apparatus main body 100), the number of the additional feeders 103 that can be added is limited. Thus, a user's demand in which images should be formed on various sheets with different sizes and types cannot be met.

SUMMARY OF THE INVENTION

[0013] The present invention has been devised in view of such a current situation, and it is an object of the present invention to provide an image forming apparatus that can form images on various sheets while controlling cost increase as low as possible.

[0014] Another object of the present invention is to provide an image forming apparatus in which a plurality of feeders each comprising a sheet containing portion and a sheet feeding portion for feeding a sheet can be added in series in an apparatus main body, including a main body side driving portion provided in the apparatus main body, and a drive feeder that is added in a predetermined position among the plurality of added feeders, in which a feeder adjacent to the apparatus main body among the plurality of added feeders is driven by the main body side driving portion, and in which the drive feeder and a feeder adjacent to the drive feeder are driven by the driving portion.

[0015] Still another object of the present invention is to provide an image forming apparatus including an apparatus main body provided with an image forming portion, a plurality of feeders which are stacked below the apparatus main body, a sheet feeding cassette for containing sheets and a pick-up roller for delivering a sheet from the sheet feeding cassette which are provided in the respective feeders, a main body side motor provided in the apparatus main body, a gear train for transmitting a driving force of the main body side motor to the pick-up roller of the feeder provided adjacently below the apparatus main body, a drive feeder which is provided among the stacked plurality of feeders and has a feeder side motor, and a gear train for transmitting a driving force of the feeder side motor to the pick-up roller of a feeder provided adjacently below the drive feeder.

[0016] These and other objects and advantages of the invention may be readily ascertained by referring to the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a view showing a schematic structure of an image forming apparatus in accordance with a first embodiment of the present invention;

[0018]FIG. 2 is a perspective view showing a state in which an apparatus main body of the image forming apparatus and a feeder are connected or the feeders are connected with each other;

[0019]FIG. 3 is a view showing the image forming apparatus and driving portions of a permanent feeder and additional feeders provided in the image forming apparatus;

[0020]FIGS. 4A and 4B are views showing a part of a sheet feeding operation in the permanent feeder or the additional feeders;

[0021]FIGS. 5A and 5B are views showing the remaining parts of the sheet feeding operation in the permanent feeder or the additional feeders;

[0022]FIG. 6 is a perspective view showing a structure of a drive transmission mechanism of a sheet feeding portion of the permanent feeder or the additional feeders;

[0023]FIG. 7 is a top plan view showing a structure of the drive transmission mechanism of the sheet feeding portion of the permanent feeder or the additional feeders;

[0024]FIG. 8 is a side view showing a structure of the drive transmission mechanism of the sheet feeding portion of the permanent feeder or the additional feeders;

[0025]FIG. 9 is a view showing a state in which feeders are added in an image forming apparatus in accordance with a second embodiment of the present invention;

[0026]FIG. 10 is a view showing a state in which feeders are added in an image forming apparatus in accordance with a third embodiment of the present invention;

[0027]FIG. 11 is a view showing a state in which feeders are added in a conventional image forming apparatus; and

[0028]FIG. 12 is a view showing another state in which a feeder is added in the conventional image forming apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Embodiments of the present invention will be hereinafter described in detail with reference to the accompanying drawings.

[0030]FIG. 1 is a view showing a structure of an image forming apparatus in accordance with a first embodiment of the present invention.

[0031] In the figure, reference numeral 1 denotes an image forming apparatus. This image forming apparatus 1 includes an apparatus main body 50 and an auto document feeder (hereinafter referred to as ADF) 2 mounted on the upper surface of the apparatus main body 50. Here, a scanner portion 6 functioning as an image reading portion is provided in the uppermost part of the apparatus main body 50. An image forming portion 3 is arranged inside the apparatus main body 50.

[0032] Moreover, in the lower part of the apparatus main body 50, there is arranged a sheet conveying portion 5 provided with a registration roller 4 and the like for conveying a sheet, which is fed from a multi sheet feeding portion 7, or a permanent feeder 51 or additional feeders 52 to 54 discussed below, to the image forming portion 3.

[0033] When a start button (not shown) is pressed in the image forming apparatus 1 of such a structure, reading of an original G by the scanner portion 6 is started first. Thereafter, a toner image is formed in the image forming portion 3 based on image information of the read original G. This toner image is transferred to a sheet S fed from the multi sheet feeding portion 7, the permanent feeder 51 or the additional feeders 52 to 54.

[0034] The sheet S having the toner image transferred thereon is conveyed to a fixing device 8, and the transferred toner image is fixed on the sheet S by the fixing device 8. Then, after the toner image is fixed in this way, the sheet S is discharged on a discharge tray 9.

[0035] Incidentally, this image forming apparatus 1 is constituted to be able to mount a plurality of stages (four stages in this embodiment) of the feeders 51 to 54, in which 250 sheets S can be contained, below the apparatus main body 50. In addition, each of the feeders 51 to 54 is constituted such that it can be completely separated from the apparatus main body 50. In case that the feeders 51 to 54 are mounted (added) in the apparatus main body 50, the apparatus main body 50 and the feeder 51 are connected or the feeders 51 to 54 are connected with each other by positioning pins 61 and 62 and coupling members (not shown) as shown in FIG. 2.

[0036] Then, since the apparatus main body 50 and the feeders 51 to 54 are separably constituted in this way, flexibility and expandability as a product can be increased such as allowing connection of another feeder capable of containing 500 sheets or providing only the multi sheet feeding portion 7 in a standard model (apparatus main body 50).

[0037] Further, in this embodiment, in order to meet a wide range of demands of users, for example, one feeder 51 is fixed to and permanently installed in the apparatus main body 50 in the image forming apparatus 1 and, at the same time, three additional feeders 52 to 54 can be added as an option.

[0038] Each of the feeders 51 to 54 includes a sheet feeding cassette 10 functioning as a sheet containing portion, picking-up means for picking the sheets S up contained in the sheet feeding cassette 10 individually from an uppermost sheet S1, a separating portion for separating the sheets picked up by the pick-up means individually, and a convey roller pair 24 and 25 for conveying the sheets separated by the separating portion.

[0039] The pick-up means has a pick-up roller 21 of a substantially half moon shape, and the separating portion includes a feed roller 22 rotating in a direction of delivering a sheet and a retard roller 23 to which a driving force for rotating in a direction of returning the sheet is transmitted via a torque limiter (not shown) coaxially provided. Sheet feeding portions 51A to 54A are constituted by these pick-up means, separating portions, convey roller pairs 24 and 25 and the like.

[0040] The sheet feeding cassette 10 is provided with a frame body made of ABS resin or the like, an intermediate plate 12 functioning as a sheet stacking stand attached to the frame body rotatably around a fulcrum 13 a, a compression coil spring 13 for pushing up the intermediate plate 12 in the direction of the pick-up roller 21, and a pair of separation claws 11 provided at a leading end corner of the sheet S in order to pick separate sheets up by the pick-up roller 21 individually. Further, the separation claws 11 become upper regulating means for regulating upward movement of the sheet S resisting an elastic force of the compression coil spring 13 when the sheet S is in a standby state. The sheet feeding cassette 10 is provided such that it can be pulled out to the front side of each of the feeders 51 to 54, that is, the side where the image forming apparatus 1 is operated (direction vertical to the sheet surface of FIG. 1).

[0041] In addition, each of the feeders 51 to 54 is provided with a conveying path for conveying a sheet delivered from the feeder arranged below it upward. The conveying path is provided such that it can be opened and closed for jam treatment as shown by an alternate long and two short dashes line of FIG. 1.

[0042] Then, in forming an image, the sheets S contained in the sheet feeding cassette 10 are separated individually by the pick-up roller 21, the separation claws 11 and the separating portion, and thereafter conveyed to the image forming portion 3 via the convey roller pair 24 and 25 and the conveying path.

[0043]FIG. 3 shows a mechanism for transmitting a driving force to such feeders 51 to 54. In the figure, reference numeral 55 denotes a main motor functioning as a main body side driving portion provided in the apparatus main body 50. This main motor 55 is for driving the sheet conveying portion 5 provided with a registration roller and the like, a photosensitive drum, a transfer roller and the like of the image forming portion 3, the fixing device 8, a discharge roller for discharging a sheet, and the like, in the image forming apparatus main body 50. Reference numeral 57 denotes a transmission gear constituting a relay portion provided in the feeder (hereinafter referred to as permanent feeder) 51 that is fixed to and permanently installed in the apparatus main body 50, and 58 denotes a drive transmission gear train functioning as a main body side transmitting portion provided in the apparatus main body 50. A driving force of the main motor 55 is transmitted to the transmission gear 57 of the permanent feeder 51 via this drive transmission gear train 58.

[0044] In addition, reference numeral 32 denotes an input gear functioning as a drive transmitting portion for meshing with the transmission gear 57 and transmitting a driving force of the main motor 55 to the sheet feeding portion 51A of the permanent feeder 51. When the transmission gear 57 rotates by the driving force of the main motor 55, the input gear 32 rotates following it and the sheet feeding portion 51A is driven.

[0045] Incidentally, a first additional feeder 52 provided optionally immediately below this permanent feeder 51 includes the transmission gear 57 and the input gear 32 as in the permanent feeder 51. In case that this first additional feeder 52 is added immediately below the permanent feeder 51, the input gear 32 of the permanent feeder 51 and the transmission gear 57 of the first additional feeder 52 mesh with each other.

[0046] That is, in case that the first additional feeder 52 is added, the input gear 32 of the first additional feeder 52 rotates via the transmission gear 57 by the main motor 55 provided in the apparatus main body 50, and the sheet feeding portion 52A is driven. In this way, a driving force is supplied to the permanent feeder 51 and the first additional feeder 52 from the main motor 55 provided in the apparatus main body 50.

[0047] On the other hand, a second additional feeder 53 functioning as a drive feeder of the present invention added in a position immediately below the first additional feeder 52 whose sheet feeding portion is driven by the main motor 55, which is a predetermined position, includes a stepping motor 56 functioning as a driving portion. Rotation of this stepping motor 56 is transmitted to the input gear 32 via an idler gear 59, whereby a sheet feeding portion 53A of the second additional feeder 53 is driven.

[0048] A third additional feeder 54 is added immediately below the second additional feeder 53. Here, the third additional feeder 54 that is a feeder adjacent to the second additional feeder 53 is provided with the input gear 32 and the transmission gear 57 as in the already described permanent feeder 51 and first additional feeder 52.

[0049] Then, in case that this third additional feeder 54 is added immediately below the second additional feeder 53, the input gear 32 of the second additional feeder 53 and the transmission gear 57 of the third additional feeder 54 mesh with each other. Consequently, when the stepping motor 56 of the second additional feeder 53 rotates, the input gear 32 rotates via the transmission gear 57, and the sheet feeding portion 54A is driven.

[0050] In this way, in case that a sheet is fed from the third additional feeder 54, a driving force is transmitted to the input gear 32 from the stepping motor 56 via the idler gear 59, whereby sheet feed driving is performed as described above. That is, in case that a sheet is fed from the third additional feeder 54, a driving force is supplied to the transmission gear 57 of the third additional feeder 54 via the input gear 32 of the second additional feeder 53, whereby the third additional feeder 54 can perform a sheet feeding operation.

[0051] Next, a drive transmission mechanism of the sheet feeding portions 51A to 54A of the feeders 51 to 54 will be described with reference to FIGS. 6 to 8. FIG. 6 is a perspective view of the drive transmission mechanism, FIG. 7 is a plan view of the drive transmission mechanism viewed from above, and FIG. 8 is a view in an arrow X direction of FIG. 6. Further, in this embodiment, the sheet feeding portions 51A to 54A of the feeders 51 to 54 have the identical structure as shown in FIG. 1, and drive transmission mechanisms thereof are also identical.

[0052] As already described, when a driving force is transmitted from the stepping motor 56 of the additional feeder 53 or the main motor 55 of the apparatus main body 50 via the transmission gear 57, the input gear 32 is driven counterclockwise shown by an arrow first. Then, this driving force is finally transmitted to the pick-up roller 21, the feed roller 22, the retard roller 23 and the convey roller 24 via a first clutch gear 35 and a second clutch gear 36 and an overall gear 37 that are provided coaxially.

[0053] The first clutch gear 35 has a cutout gear 35 a that meshes with a coaxially fixed pick-up gear 33 at predetermined timing in order to rotate the pick-up roller 21 and is provided with a cam portion 35 b fixed on the side of the cutout gear 35 a. A claw portion 35 c for locking the tip of a flapper 31 a of a sheet feeding solenoid 31 is formed in the cam portion 35 b. In addition, a cam lever 42 for biasing the cam portion 35 b in an arrow K direction of FIG. 6 by a torsion coil spring 43 is in pressed contact with the end of the cam portion 35 b.

[0054] The second clutch gear 36 includes a cutout gear 36 a meshing with a small diameter gear portion 32 a of the input gear 32 and a cutout gear 36 b meshing with a coaxially fixed feed gear 34 at predetermined timing in order to rotate the feed roller 22. The cutout gear 36 a and the cutout gear 36 b are integrally formed. The first clutch gear 35 and the second clutch gear 36 integrally rotate coaxially by the fitting of a boss and a boss hole provided on not-shown sides of them.

[0055] The overall gear 37 is arranged coaxially with the clutch gears 35 and 36 but is provided to be freely rotatable and meshes with the small diameter gear portion 32 a of the input gear 32, whereby a driving force is transmitted to the overall gear 37 from the input gear 32. The overall gear 37 can transmit a driving force to a retard gear 39 fixed coaxially with the retard roller 23 and a convey roller gear 41 fixed coaxially with the convey roller 24 via idler gears 38 and 40. When the main motor 55 or the stepping motor 56 is rotating, the overall gear 37 always transmits a driving force to the retard roller 23 and the convey roller 24.

[0056] Further, the feed roller 22 and the retard roller 23 are attached to cantilever shafts 22 a and 23 a of front side support, respectively, as shown in FIG. 6, thereby being arranged such that they can be easily replaced.

[0057] Here, when the tip of the flapper 31 a of the sheet feeding solenoid 31 is locked by the claw portion 35 c of the cam portion 35 b of the clutch gear 35 as shown in FIG. 8 and the flapper 31 a is stopped resisting a press-contacting force of the cam lever 42, each of the clutch gears 35 and 36 is held such that a non-tooth part of the cutout gear 35 a of the first clutch gear 35 is opposed to the pick-up gear 33 and non-tooth part of the cutout gear 36 a of the second clutch gear 36 is opposed to the input gear 32.

[0058] Further, in this state, that is, when a driving force is not inputted in the pick-up gear 33, the pick-up roller 21 is in standby in a position where a notch part is opposed to the sheet S by not-shown biasing means (the state shown in FIG. 4A).

[0059] Driving of the main motor 55 of the apparatus main body 5 and the stepping motor 56 provided in the additional feeder 53 and ON/OFF of the sheet feeding solenoid 31 are controlled by a control portion C (shown in FIG. 1) provided in the apparatus main body 5.

[0060] Next, an operation of this drive transmission mechanism will be described. When a sheet feeding instruction is issued in an initial state, first, the sheet feeding solenoid 31 is excited and the flapper 31 a comes off the claw portion 35 c of the first clutch gear 35. Then, the first clutch gear 35 and the second clutch gear 36 start rotating clockwise integrally by an action of the cam lever 42. Then, after the first clutch gear 35 and the second clutch gear 36 start rotating in this way, the cutout gear 36 a of the second clutch gear 36 meshes with the input gear 32, whereby a driving force is transmitted to the first clutch gear 35 and the second clutch gear 36.

[0061] Next, when a driving force is transmitted to the first clutch gear 35 and the second clutch gear 36 in this way, the cutout gear 35 a of the first clutch gear 35 meshes with the pick-up gear 33 at predetermined timing soon, whereby the pick-up roller 21 starts rotating. In addition, the cutout gear 36 b of the second clutch gear 36 meshes with the feed gear 34 at predetermined timing, and the feed roller 22 starts rotating following this.

[0062] Subsequently, sheets are delivered by the rotation of the pick-up roller 21 and separated by the separation claws 11. Sheets that were not separated by the separation claws 11 are surely separated individually between the feed roller 22 and the retard roller 23 to be sent to the convey roller pair 24 and 25 and supplied to the image forming portion 3 of the apparatus main body 50 via a conveying path.

[0063] In this way, according to this drive transmission mechanism, synchronized control of the pick-up roller 21 and the forward rotation feed roller 22 and one rotation control of the pick-up roller 21 becomes possible simply by controlling one electric component, the sheet feeding solenoid 31.

[0064] Next, a sheet feeding operation of the feeders 51 to 54 constituted as described above will be described with reference to FIGS. 4A and 4B and FIGS. 5A and 5B.

[0065] In each of the feeders 51 to 54, when a sheet feeding instruction is issued to a predetermined feeder in which sheets to be supplied are contained among the feeders 51 to 54 from the control portion C of the apparatus main body 50, the main motor 55 or the stepping motor 56 rotates and, at the same time, the sheet feeding solenoid 31 of the feeder to which the sheet feeding instruction is issued is excited (turned ON). Consequently, first, the corresponding pick-up roller 21 of the feeder starts rotating from a position shown in FIG. 4A by the rotation of the motor 55 or 56 and thereafter abuts the uppermost sheet S1 among the sheets S stacked on an intermediate plate 2 as shown in FIG. 4B.

[0066] Further, the pick-up rollers 21 of the other feeders to which a sheet feeding instruction is not issued from the control portion C do not rotate by the clutch mechanisms 35 and 36 that use cutout gears provided between the input gears 32 of the feeders 51 to 54 and the sheet feeding portions 51A to 54A.

[0067] Next, when the pick-up roller 21 further rotates in this state, the leading end of the uppermost sheet S1 comes off the separation claws 11 to enter the separating portion as shown in FIG. 5A. Here, the feed roller 22 constituting this separating portion has already started rotating synchronously with one rotation of the pick-up roller 21, and a driving force for rotating the retard roller 23 in a direction for returning a sheet is transmitted to the retard roller 23 via a power transmission mechanism, which idles when a torque of a predetermined value or more is applied as a load, a so-called torque limiter.

[0068] Thus, when one sheet S1 is fed to the separating portion, a load torque applied to the torque limiter from the sheet S1 via the retard roller 23 exceeds the predetermined value, and the torque limiter idles. Consequently, the retard roller 23 is driven to rotate by the sheet S1 conveyed by the feed roller 22.

[0069] Then, the sheet S1 is conveyed to the convey roller pair 24 and 25 in the downstream by the rotation of the feed roller 22. Thereafter, the feed roller 22 is driven to rotate by the sheet S1 conveyed to the convey roller pair 24 and 25 in the downstream.

[0070] Further, if sheets are not completely separated by the separation claws 11 and two or more sheets are fed to the separating portion, a frictional force between the sheets is applied to the torque limiter as a load torque via the retard roller 23. Since this value is equal to or less than the predetermined value, the torque limiter does not idle, and the retard roller 23 rotates in a direction for returning a sheet to the sheet feeding cassette 10. Consequently, the sheets S can be prevented from being doubly fed to the downstream side by the separating portion even if the sheets are failed to be separated by the separation claws 11.

[0071] In this way, the sheet feeding solenoid 31 provided in any one of the permanent feeder 51 or the additional feeders 52 to 54 containing sheets to be supplied is controlled, whereby the sheet S can be selectively conveyed to the image forming portion 3 from the permanent feeder 51 or the additional feeders 52 to 54.

[0072] As described above, in this embodiment, the sheet feeding portion 54A of the third additional feeder 54 located immediately below the second additional feeder 53 is also driven by the stepping motor 56 of the second additional feeder 53, whereby images can be formed on various sheets while controlling cost increase as low as possible. Accordingly, multi sheet feeding becomes possible without increasing the capacity of the main motor 55 provided in the apparatus main body 5. As a result, it becomes possible to increase a degree of freedom and expandability as a product.

[0073] Incidentally, as already described, as feeders to be mounted in the apparatus main body 50, there are two types, namely, the second additional feeder 53 provided with the stepping motor 56 and the permanent and additional feeders 51, 52 and 54 driven by the main motor 55 of the apparatus main body 50 or the stepping motor 56 of the second additional feeder 53.

[0074] Here, as already described, the sheet feeding portions 51A to 54A of the feeders 51 to 54 have a common structure, and the input gear 32 is provided in each of the feeders 51 to 54. That is, the feeders 51, 52 and 54 that receive supply of a driving force have the completely identical structure.

[0075] Moreover, in this embodiment, the stepping motor 56 of the second additional feeder 53 is constituted to be interchangeable with the transmission gear 57. Consequently, if the transmission gear 57 is attached instead of the stepping motor 56, the second additional feeder 53 comes to have the completely identical structure as the feeders 51, 52 and 54 that receive supply of a driving force.

[0076] In this way, the stepping motor 56 and the transmission gear 57 are constituted to be interchangeable with each other, whereby the feeders becomes convertible with each other. As a result, common use of parts and units is facilitated, and a feeder contributing to cost reduction and re-manufacturing (REM) significantly and the image forming apparatus 1 provided with the same can be provided.

[0077] Next, a second embodiment of the present invention will be described.

[0078]FIG. 9 is a view showing a state in which feeders are added in an image forming apparatus in accordance with this embodiment.

[0079] In this embodiment, a permanent feeder 61 that can contain 250 sheets and five stages of additional feeders 62 to 66 that can contain 250 sheets are mountable below an apparatus main body 60 of the image forming apparatus. Here, when added, the additional feeder 63 second from the top and the additional feeder 65 second from the bottom are provided with a stepping motor 68 functioning as a driving portion, respectively.

[0080] Then, when mounted and added below the apparatus main body 60, the permanent feeder 61 and the additional feeder 62 at the top, the third additional feeder 64, and the additional feeder 66 at the bottom receive supply of a driving force from a main motor 67 of the apparatus main body 60, the stepping motor 68 of the second additional feeder 63, and the stepping motor 68 of the additional feeder 65 second from the bottom, respectively. Consequently, a universal multi sheet feeding structure can be realized as a product without causing cost increase.

[0081] In addition, in this embodiment, again, two kinds of feeders, namely, those provided with the stepping motor 68 and the input gear (see FIG. 3) and those provided with the transmission gear (see FIG. 3) instead of the stepping motor 68 and the input gear are used as feeders. On the other hand, the sheet feeding portions of these feeders 61 to 66 are made identical and the stepping motor 68 and the transmission gear are interchangeably constituted.

[0082] Consequently, as in the already described first embodiment, the feeders becomes convertible with each other if the stepping motor 68 and the transmission gear are interchanged. As a result, common use of parts and units is facilitated, and a feeder contributing to cost reduction and re-manufacturing (REM) significantly and the image forming apparatus 1 provided with the same can be provided.

[0083] Further, in the second embodiment, the structure of the image forming apparatus and the structures of the sheet feeding portion, the driving portion, the sheet feeding cassette and the like provided in the feeders 61 to 66 are the same as those in the first embodiment.

[0084] Next, a third embodiment of the present invention will be described.

[0085]FIG. 10 is a view showing a state in which feeders are added in an image forming apparatus in accordance with this embodiment.

[0086] In this embodiment, one permanent feeder 71 that can contain 500 sheets and two stages of additional feeders 72 and 73 that can contain 500 sheets are mountable. Here, when added, the additional feeder 72 first from the top is provided with a stepping motor 75 functioning as a driving portion.

[0087] Then, when mounted onto the apparatus main body 70, the permanent feeder 71 and the second additional feeder 73 receive supply of a driving force from a main motor 74 of the apparatus main body 70 and the stepping motor 75 of the first additional feeder 72, respectively. Consequently, a universal multi sheet feeding structure can be realized as a product without causing cost increase.

[0088] In addition, in this embodiment, two kinds of feeders, namely, one provided with the stepping motor 75 and the input gear (see FIG. 3) and those provided with the transmission gear (see FIG. 3) instead of the stepping motor 75 and the input gear are also used as feeders. On the other hand, the sheet feeding portions of these feeders 71 to 73 are made in a common structure and the stepping motor 75 and the transmission gear are interchangeably constituted.

[0089] Consequently, as in the already described first and second embodiments, the feeders becomes convertible with each other if the stepping motor 75 and the transmission gear are interchanged. As a result, common use of parts and units is facilitated, and a feeder contributing to cost reduction and re-manufacturing (REM) significantly and the image forming apparatus 1 provided with the same can be provided.

[0090] Further, also in the third embodiment, the structure of the image forming apparatus and the structures of the sheet feeding portion, the driving portion, the sheet feeding cassette and the like provided in the feeders 71 to 73 are the same as those in the first embodiment.

[0091] In each embodiment described above, the two stages of feeders 51 and 52 are constituted to receive a driving force from the main motor 55 of the main body side driving portion of the apparatus main body 50. However, a plurality of feeders may be stacked below the apparatus main body 50 so as to receive a driving force of the main motor 55. In addition, in each embodiment, the one stage of feeder 54 receives a driving force from the stepping motor 56 of the additional feeder 53. However, a plurality of feeders may be stacked below the additional feeder 53 so as to receive a driving force of the stepping motor 56. Further, a driving force of the stepping motor 56 may be transmitted to feeders provided above the additional feeder 53.

[0092] In addition, the feeder provided with one sheet feeding portion has been described. However, the present invention is not limited to this, and a feeder having a structure with a plurality of sheet containing portions and sheet feeding portions arranged therein may be used.

[0093] Further, the feeder provided immediately below the apparatus main body 50 has been described as the permanent feeder fixed to the apparatus main body 50. However, the feeder may be an additional feeder that is not fixed to the apparatus main body 50.

[0094] Moreover, the structure in which the additional feeder provided with the driving portion drives the additional feeder immediately below it has been described. However, the present invention is not limited to this, and the additional feeder provided with the driving portion may drive an additional feeder immediately above it. Furthermore, the additional feeder provided with the driving portion may drive a plurality of additional feeders. In addition, an additional feeder may be constituted to be added in a horizontal direction of the image forming apparatus.

[0095] While the described embodiment represents the preferred for the present invention, it is to be understood that modifications will occur to those skilled in that art without departing from the spirit of the invention. The scope of the invention is therefore to be determined solely by the appended claims. 

What is claimed is:
 1. An image forming apparatus wherein a plurality of feeders each including a sheet containing portion and a sheet feeding portion for feeding a sheet can be added in series in an apparatus main body, comprising: a main body side driving portion provided in said apparatus main body; and a drive feeder added in a predetermined position among said plurality of added feeders, wherein a feeder adjacent to said apparatus main body among said plurality of added feeders is driven by said main body side driving portion, and wherein said drive feeder and a feeder adjacent to said drive feeder are driven by said driving portion.
 2. An image forming apparatus according to claim 1, wherein, in case that another feeder is connected between said feeder adjacent to said apparatus main body and said drive feeder, said another feeder is driven by said main body side driving portion.
 3. An image forming apparatus according to claim 1, wherein, in case that another feeder is further connected to said feeder adjacent to said drive feeder, said another feeder is driven by said driving portion provided in said drive feeder.
 4. An image forming apparatus according to claim 1, wherein said feeders and said drive feeder comprise a sheet containing portion for containing sheets and a sheet feeding portion for feeding a sheet from said sheet containing portion, and drive said sheet feeding portion by a driving force from said main body side driving portion or said driving portion to feed a sheet.
 5. An image forming apparatus according to any one of claims 1 to 4, wherein said feeders other than said drive feeder provided with said driving portion are constituted in common.
 6. An image forming apparatus according to claim 4, wherein said drive feeder comprises a drive transmitting portion for driving said sheet feeding portion by a driving force of said driving portion provided in said drive feeder and transmitting a driving force to said feeder adjacent to said drive feeder, and wherein said adjacent feeder comprises a relay portion to which a driving force of said driving portion is transmitted via said drive transmitting portion and transmits the driving force received by said relay portion to said sheet feeding portion.
 7. An image forming apparatus according to claim 6, wherein a feeder having a same structure as a structure of said feeder driven by said main body side driving portion of said apparatus main body is connected to said feeder, and a driving force from said main body side driving portion is sequentially transmitted to said feeders via said relay portion and said drive transmitting portion.
 8. An image forming apparatus according to claim 4, wherein said feeder which is adjacent to said apparatus main body and is driven by said main body side driving portion comprises a relay portion to which a driving force from said main body side driving portion is transmitted and a drive transmitting portion for transmitting the driving force received by said relay portion to said sheet feeding portion, and said drive transmitting portion has the same structure as a structure of a drive transmitting portion of said drive feeder and a drive transmitting portion of said feeder driven by said driving portion of said drive feeder.
 9. An image forming apparatus according to claim 6, wherein said driving portion of said drive feeder is made interchangeable with said relay portion of a feeder which is adjacent to said drive feeder and is driven by said driving portion.
 10. An image forming apparatus according to claim 1, wherein said feeders are stacked vertically below said apparatus main body, and said drive feeder is arranged below said feeder driven by said main body side driving portion.
 11. An image forming apparatus including: an apparatus main body provided with an image forming portion; a plurality of feeders which are stacked below said apparatus main body; a sheet feeding cassette for containing sheets and a pick-up roller for delivering a sheet from said sheet feeding cassette which are provided in said respective feeders; a main body side motor provided in said apparatus main body; a gear train for transmitting a driving force of said main body side motor to said pick-up roller of said feeder provided adjacently below said apparatus main body; a drive feeder provided among said stacked plurality of feeders and has a feeder side motor; and a gear train for transmitting a driving force of said feeder side motor to said pick-up roller of a feeder provided adjacently below said drive feeder.
 12. An image forming apparatus according to claim 11, wherein said feeder adjacent to said apparatus main body and said feeder adjacent to said drive feeder have a common structure.
 13. An image forming apparatus according to claim 11, wherein each of said feeders has a feed roller and a retard roller for separating sheets delivered by said pick-up roller individually, a convey roller for conveying the sheet separated individually, and a clutch for transmitting or not transmitting a driving force to each roller, and said clutch is controlled by a control portion provided in said apparatus main body.
 14. An image forming apparatus according to claim 13, wherein said gear trains comprise transmission gears for receiving a driving force from said apparatus main body or from said plurality of feeders and input gears meshing with said transmission gears, and a driving force is transmitted to said pick-up roller and said feed roller from said input gears via said clutch.
 15. An image forming apparatus according to claim 14, wherein said feeder side motor of said drive feeder and said transmission gears of said plurality of feeders are made interchangeable. 